1. Technical Field
The invention relates to: an image stabilization unit that is suitably used, as an image stabilization mechanism, in an imaging device such as a digital camera and a camera built-in cellular phone; an image stabilization device having the image stabilization unit; and an imaging apparatus having the image stabilization device.
2. Description of the Related Art
Conventionally, in order to suppress disturbance in a captured image due to vibration of a user's hand or the like, various image stabilization mechanisms have been used in digital cameras and the like (see JP Hei. 7-274056 A, JP 2005-326807 A (corresponding to US 2005/0225646 A) and Japanese Patent No. 2612371).
Some of the image stabilization mechanisms adopt a system called a gimbal mechanism so that a hold module is freely rotatable in a yaw direction and in a pitch direction.
However, in a gimbal mechanism disclosed in JP Hei. 7-274056 A, it is necessary to provide rotary joints or the like that rotate freely in four positions, that is, upper, lower, left, and right positions in the hold module. Accordingly, the size of the image stabilization mechanism tends to increase. In addition, excessive miniaturization of the image stabilization mechanism causes such a problem that bearing portions of the rotary joints or the like are weakened.
Thus, unpublished earlier Japanese patent application Nos. 2006-269712, 2006-269713, 2006-269714 and 2006-269715, filed by Fujinon Corporation, propose a drive structure that supports a pivot point that is one point on an outer circumference of a hold module drives a hold module so as to freely swing and that drives the hold module through first and second drive points that are respectively separate from the pivot point in first and second directions that are different from each other. When this drive structure is implemented, it becomes possible to downsize the image stabilization unit. As a result, it also becomes possible to build the image stabilization unit in a mobile device.
FIG. 11 is a diagram showing an image stabilization unit 2 of another example that is designed to be downsized in order to build it in a mobile device.
FIG. 11 shows a diagram of the image stabilization unit 2 of the other example, when it is viewed from an upward right direction. FIG. 11 shows a hold module 20 that holds an imaging lens 10 and a support body 21 that supports the hold module 20 at a pivot point PB so as to freely swing, which are components of the image stabilization unit 2.
As shown in FIG. 11, in order to allows the hold module 20 to freely rotate in the yaw direction of the hold module 20, the support body 21 is provided with a first drive section 23 along a right side surface of the hold module 20. Also, in order to allow the hold module 20 to freely rotate in the pitch direction, the support body 21 is provided with a second drive section 24 along a bottom surface of the hold module 20.
The first drive section 23 and the second drive section 24 are respectively provided with coils 234 and 244 and magnets 233 and 243. The magnets 233 and 243 are respectively fixed to support members 210 and 211 extending from the support body 21 along the right side surface of the hold module 20 and the bottom surface of the hold module 20.
On the other hand, the coils 234 and 244 are connected to arms ARM1 and ARM2 that are held to be freely movable with respect to the support body 21. Front end portions of the arms ARM1 and ARM2 are engaged with the hold module 20 at drive points D1 and D2.
These engagements are implemented by pressing sphere-shaped engagement members Q1 and Q2 disposed in the drive points D1 and D2 on the arm ARM1 and ARM2 sides against concave portions provided in the drive points D1 and D2 on the hold module 20 side using springs SP1 and SP2.
With the configuration shown in FIG. 11, for example, when the image stabilization unit is installed in an image stabilization device and when current signals sent from a control section of the image stabilization unit current causes current to flow through the coils 234 and 244, electromagnetic forces act between the coils 234 and 244 and the magnets 233 and 243, to move the coils 234 and 244. Thereby, the arms ARM1 and ARM2 are moved together with the coils 234 and 244, and the hold module 20 is individually driven at the two drive points D1 and D2. As a result, the hold module 20 swings as a whole. The two coils 234 and 244 shown in FIG. 11 are coil substrates that are substrates formed with coils thereon. The respective coil substrates are disposed to be parallel to the magnets 243 and 233. Also, the image stabilization unit shown in FIG. 11 is not one that is used for open loop control as described in JP 2006-295553 A, but one used for feedback control. Therefore, sensors, for example, hall elements HD1 and HD2 are disposed on the coil substrates so that positions of the coil substrates when the coil substrates are moved can be detected. These sensors HD1 and HD2 detect changes in magnetic forces applied from the magnets 233 and 243 when the hold module 20 is driven at the driving points D1 and D2 in accordance with movements of the coil substrates together with the arms and outputs magnitudes of the detected magnetic forces as position signals.
However, in the above-described configuration of the image stabilization unit, the front end portions of the arms ARM1 and ARM2, which are engaged with the hold module 20, are free ends. Therefore, when the hold module 20 is simultaneously driven at the two drive points (the first drive point D1 and the second drive point D2), there may be a case where movement of the arm ARM2 or ARM1 driven by one of the drive points D2 and D1 follows movement of the arm ARM1 or ARM2 driven by the other of the drive points D1 and D2. If such a case occurs, a distance between the magnet and the sensor, which is disposed on the coil substrate held by the one of the arms changes depending on the movement of the other arm. As a result, there may be a case where an output of the sensor HD1 or HD2 disposed on the coil substrate held by the arm becomes unstable.
If the outputs of these sensors HD1 and HD2 become unstable, when the image stabilization unit is installed in the image stabilization device, the position of the coil substrate is not correctly detected by the control section of the image stabilization device. As a result, posture control of the hold module is not performed accurately.